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I have a weird issue with my UM2. I have printed with different filaments lately and killed a few PTFE couplers. That's fine because I expected it. But now I have a brand new glass reinforced coupler that looks like this after only 10 hours of printing with PLA:

I used this spring replacement. Could this hardcore deformation happen so soon if there is too much pressure on the coupler?

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On the opposite, I also noticed you need to check the pressure on the spring replacement now and then as it will get more loose over time (so check by turning the hot-end-isolator and feel the pressure)

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That black stuff is probably well-cooked PLA and not related to the teflon part.

Make sure it's really a problem:

remove nozzle (do you have an olsson block? if not then I don't know how to test this), remove filament from head (but you can leave it in the bowden), remove bowden from head. Let nozzle cool to below 50c, then insert filament through the whole head assembly, teflon part and all and feel how much friction there is through the teflon part.

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Really? I guess I've never seen it happen so I don't know what to look for. I could interpret the shadows several different ways inside the ptfe. I'm not an expert on failed ptfe because I've never had one fail.

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Really? I guess I've never seen it happen so I don't know what to look for. I could interpret the shadows several different ways inside the ptfe. I'm not an expert on failed ptfe because I've never had one fail.

You might have seen this post already but it's like a ptfe coupler master class from anders

Edited February 26, 2016 by Guest

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Really? I guess I've never seen it happen so I don't know what to look for. I could interpret the shadows several different ways inside the ptfe. I'm not an expert on failed ptfe because I've never had one fail.

Man lucky you. I just threw away a hand full of failed couplers - all with dents inside...

Maybe @ultiarjan ist right, maybe the pressure was too high. But still - I don't think it is normal for a coupler to die that fast, even under greater pressure.

@neotko: Sadly the dent is pretty deep so I'd have to cut a lot off the coupler. I have the I2K chip but somehow I never had luck with it. Regardless of what I did, there was always under extrusion with it.

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Really? I guess I've never seen it happen so I don't know what to look for. I could interpret the shadows several different ways inside the ptfe. I'm not an expert on failed ptfe because I've never had one fail.

Man lucky you. I just threw away a hand full of failed couplers - all with dents inside...

Maybe @ultiarjan ist right, maybe the pressure was too high. But still - I don't think it is normal for a coupler to die that fast, even under greater pressure.

@neotko: Sadly the dent is pretty deep so I'd have to cut a lot off the coupler. I have the I2K chip but somehow I never had luck with it. Regardless of what I did, there was always under extrusion with it.

Maybe you just need the metal thingy that replaces the spring, or the printed version.

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The only way I can see it failing that fast is if the temperature is _way_ off or there is some crazy amount of pressure on it. If the temperature was way off I would expect to see some sort of problem with the print as well like excessive oozing, "bubbling" etc. But you're too much of a veteran to make something like that pass by.

Excessive pressure could be the problem I guess. Ultimaker was very clear with us that the distance between the two metal plates was quite critical on the UM2+ to keep the coupler in place just right.

It's a bit strange no doubt.

Also @gr5, you must be one lucky SOB to not have seen a ruined PTFE yet. I've seen... a "few"...

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The only way I can see it failing that fast is if the temperature is _way_ off or there is some crazy amount of pressure on it. If the temperature was way off I would expect to see some sort of problem with the print as well like excessive oozing, "bubbling" etc. But you're too much of a veteran to make something like that pass by.

Veteran Blush (anime style)

The temp sensor is brand new and I also performed PID Autotune. I didn't notice anything unusual with the filament.

Excessive pressure could be the problem I guess. Ultimaker was very clear with us that the distance between the two metal plates was quite critical on the UM2+ to keep the coupler in place just right.

It's a bit strange no doubt.

Also @gr5, you must be one lucky SOB to not have seen a ruined PTFE yet. I've seen... a "few"...

The thing is - what is the right pressure? I printed the spring replacement and then screw in the metal collet a lot so there was barely any distance between the collet and the coupler. I did this in order to lessen the pressure on the coupler enforced by the spring replacement.

Not sure what to do now. I have a new coupler. Try it with the spring replacement and screw it in to barely have any pressure or just use the regular spring?

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Ultimaker uses a simple "tool" (basically a simple spacer) that they put between the plates before tightening down so that they stop at the correct distance. I still haven't gotten one of those myself though.

That said I've been naughty and taken the head on my plus-machine apart and screwed it back together again and seems to work fine still.

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Hm when I think about it, the right distance between the two metal plates should be already set when they are screwed together. So when I leave out the spring (or spring replacement) and just screw the two plates together, the distance amounts to 17.14mm

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